Now, I don't think we can win against him, Wuxiang Qiankun or not. Even though we can copy his techniques, his stats are still superior to ours, and he is holding back on us, waiting for us to use our ace to then top it. Even if we could win, he can escape due to his superior speed once he learns what he came here to learn.
I also don't think we can run away from him. He is faster, and he takes care to avoid just that outcome. Turning his back to him is more risky than fighting him head on.
I don't see much point in talking to him and revealing anything. Our Firelordship isn't even our secret to tell, and it does not answer his questions at all. He is interested in becoming stronger, what does he care about the temple? Are we going to shock him into forgetting what the original purpose of the question was? After the initial shock wears our, he will realise he is no closer to the truth than he was, and then he will have leverage against us.
I see no point in letting him know we have the skill without a fight, either. This does not even let us test ourselves against him. Why would we surrender that easily?
Finally, zhang manxing is the least of our problems right now. I suppose it is possible that he crawls away during our fight, but that is more of Bai's problem than ours, unless we confess and there is something to prevent Bai from killing him outright.
So for me, there is only fighting and running away. Out of these, I am fine with whatever lets us leave this place alive and in one piece. I don't know what winning here after showing our hand would do for us. I am not going to kill BJ - I'd still prefer him working against zhang family.
And since I am not trying to win, I am going for the choice that I think loses less.
Well, unless we play dirty like we did in our weiqi match and use that powder against him. It is something to consider, but D does not mention it at all.